provider_conf: report missing section on error

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12663)

crypto/provider_conf.c

@@ -89,6 +89,7 @@ static int provider_conf_load(OPENSSL_CTX *libctx, const char *name,
 
     if (!ecmds) {
         CRYPTOerr(CRYPTO_F_PROVIDER_CONF_LOAD, CRYPTO_R_PROVIDER_SECTION_ERROR);
+        ERR_add_error_data(3, "section=", value, " not found");
         return 0;
     }